isEmail method
Check if a string is a valid email address.
Implementation
bool isEmail() {
if (this == null) {
throw ArgumentError('string: $this');
}
if (this!.isEmpty) {
return false;
}
return RegExp(r'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$')
.hasMatch(this!);
}